The consequences of postpartum depression (PPD) extend far beyond the mother's mental health, and can have severe detrimental effects on parenting abilities, mother-infant bonding, and infant health and development. Although Latinos are the fastest growing population group in the U.S., few studies of PPD have been conducted with Latina women. Existing studies suggest a significantly elevated vulnerability to PPD for low income ethnic minority women, which translates into an elevated risk for their children. However, most research has failed to consider the fundamental role of the newborn baby and the ability of mother-infant interactions to influence the onset and course of PPD, as well as the consequences for infant and child development. The parent grant for this supplemental proposal is evaluating a community sample of 330 low-income Mexican American new mothers from the prenatal period through the first postpartum year to assess the development of PPD, cultural-ecological factors that may either confer risk or offer protection from PPD, and the biopsychosocial process by which maternal depression influences and is influenced by mother-infant co-regulation of each other's emotions, behavior, and physiology. We propose to extend these aims by the addition of comprehensive measurement of infant temperament, attachment, and cognitive, emotional, and behavioral functioning through 2 years of age. This project takes the dynamic perspective that PPD influences infant development at the same time that infant development influences PPD. In short, a culturally-informed understanding of the impact of PPD on infant functioning has important reciprocal implications for the health and well-being of Mexican American new mothers. Collection of this additional data will enable a better understanding of the underlying mechanisms of PPD and its effects on mothers and infants, but also allows an extra year of data collection to better support the future submission of a proposal to longitudinally follow of this critical population with documented health disparity for PPD. PUBLIC HEALTH RELEVANCE: A large research literature documents the substantial detrimental public health impact of postpartum depression. Infants and children of mothers who are depressed, especially those experiencing social disadvantage, face considerable short and long-term disadvantage, including lower birth weight, poorer cognitive development, higher rates of behavioral and social problems, and more frequent emotional problems. Population birth trends and the significant mental health disparities new Hispanic mothers and their infants experience argue for the critical need for further understanding of processes affecting the development of postpartum mood disorders in low-income Mexican American women and the consequences for their children.